Emergency descent control devices are known. U.S. Pat. No. 6,131,697 teaches a rappelling rope controller which utilizes a U-shaped rod supporting three bars of circular cross section movable along the arms of the rod, and enlarged abutments on the free ends of the rod preventing removal of the bars, but no mechanism for releasing the load are present. US Patent Application No. 2010/0236863 teaches an auto-lock compact rope descent device is a bar with holes for guiding a rope used is descent, and a lever designed to pivot or move relative to the bar and compresses the opening of one of the holes. Compressing the opening increases friction and slows or stops descent.
US Patent Application No. 2012/0261212 teaches an anti-panic descender with possibility of ascent that uses a lever. US Patent Application No. 2011/0048852 teaches a descender with fall arrest and controlled rate of descent. US Patent Application No. 2009/0120720 teaches a frictionless descender for abseiling along a rope that also has a handle to control descent. These devices do not show the internal rigging of the rope, and therefore, are not as easy to inspect. Most of these devices provide two loops in a threaded rope, and use a breaking action provided by the lever to slow the movement.